There are many circumstances in which it is desired to use colored or metallic foils, including gold, silver, red, and holographic foil materials, on substrates, including in the manufacture of plastic components, and in advertising where printing is desired to be particularly decorative. The present approaches to producing substrates with colored or metallic foil printing thereon is both extremely slow and extremely limited in application. Even with the most effective utilization of conventional equipment, production speeds on the order of only about 20 feet per minute are possible. Even more significantly, however, the images are typically fixed in nature (such as raised plate), or there is only a very limited pattern variation, such as produceable from a numbering machine or the like.
According to the present invention, it is possible for the first time to produce advertising printing or the like with colored or metallic foils at high speed (e.g. about 100 feet per minute or greater), and with almost infinite variety. This is accomplished, according to the invention, by utilizing a computer controlled print engine which prints toner particles on-line, in any desired, variable, pattern (words, images, and/or other indicia), the toner typically having a thermoplastic component. The invention also is accomplished by utilizing a completely rotary approach to effect the transfer of the colored or metallic foil from a foil strip to the substrate, rather than the conventional primarily reciprocal (and thus inherently speed limited) approaches, such as provided in the foil-stamping equipment produced by Kluge of Germany.
The foil utilized in the production of printed substrates according to the invention is conventional foil having a backing or a carrier film, with a release coating thereon, with the foil over the release coating, and a transfer adhesive on the exterior surface of the foil. The adhesive is brought into contact with the toner on the substrate, and by the application of heat and pressure to the foil strip the adhesive and foil are transferred to the toner, having a greater affinity for the toner than the release coating on the backing. The receptability of the toner to the adhesive and foil may be enhanced by heating the toner, as with an infrared heater, just prior to the application of heat and pressure to the foil strip and substrate. If desired this effect can be enhanced further by heating an impression cylinder over which the substrate continuously travels during processing.
Transfer is effected utilizing a transfer cylinder and an impression cylinder. One of the cylinders is of a rigid metal material, while the other is hard rubber or the like (e.g. heated silicone, known per se for this purpose). The transfer cylinder has a plurality of circumferentially spaced heated raised portions, and the transfer cylinder is continuously rotated with the spaced raised heated portions periodically coming into contact with the foil strip and applying pressure at the nip between the transfer cylinder and the impression cylinder. Utilizing this rotary principle, speeds of operation in excess of about 100 feet per minute (e.g. at least about 120 feet per minute, and even as high as about 300 feet per minute) are possible.
The print engine, such as a MIDAX print engine, for applying the toner pattern according to the invention is computer controlled and can provide a virtually infinite variety of variable patterns, including words, images, and/or virtually any type of indicia, on the substrate. The substrate is typically paper, and is typically in web form, although it also may be in sheet form.
According to one aspect of the present invention, a method of producing a printed substrate having colored or metallic foil over at least a part of the printing is provided, comprising the following steps: (a) Printing a desired pattern on a substrate using toner having a thermoplastic component. (b) Continuously feeding the substrate to and past a transfer location. (c) Feeding a foil strip having an outer adhesive layer, a colored or metallic foil layer, and a release coated carrier, to the transfer location, with the adhesive facing the substrate. (d) Heating the toner pattern on the substrate just prior to the transfer location to make the thermoplastic component of the toner receptive to the foil and adhesive layers of the foil strip. And, (e) applying heat to the foil strip, and pressure to the foil strip and substrate, at the transfer location so as to transfer the adhesive and colored or metallic foil onto the heated toner pattern.
Step (a) is preferably practiced by variably printing the pattern utilizing a computer controlled print engine (such as a MIDAX printer), and step (b)--whether the substrate is in web or sheet form--is practiced at a speed of at least about 100 feet per minute.
According to another aspect of the present invention, a similar method is provided comprising the following steps: (a) Variably printing a desired pattern on a substrate using toner. (b) Continuously feeding the substrate to and past a transfer location. (c) Feeding a foil strip having an outer adhesive layer, a colored or metallic foil layer, and a release coated carrier, to the transfer location, with the adhesive facing the substrate. And, (d) applying heat to the foil strip, and pressure to the foil strip and substrate, at the transfer location so as to transfer the adhesive and colored or metallic foil onto the toner pattern, by passing the substrate and foil strip between an impression cylinder and a transfer cylinder, the substrate engaging the impression cylinder. The transfer cylinder preferably has a plurality of circumferentially spaced heated raised surface portions which engage the foil strip, and step (d) is further practiced by continuously rotating the transfer cylinder so that the raised heated surface portions periodically come into contact with the foil strip and exert a pressure on the strip and substrate when they do come into contact, transferring the colored or metallic foil to the printed pattern.
The invention also comprises an apparatus for producing the printed substrate according to the invention. The apparatus comprises: Means for variably printing a predetermined pattern, with toner, on the substrate. An impression cylinder mounted for rotation about a first axis. A transfer cylinder mounted for rotation about a second axis parallel to the first axis, and to define a nip between the impression cylinder and the impression cylinder. Means for continuously feeding the substrate to and past the nip between the transfer cylinder and impression cylinder, with the toner pattern on the substrate facing the transfer cylinder. Means for feeding a foil strip having an adhesive, a foil, and a backing, to the nip with the adhesive and foil facing the impression cylinder. Means for taking up the foil strip backing after passage of the foil strip through the nip. And, means for heating the transfer cylinder to facilitate transfer of the adhesive and foil from the foil strip to the toner pattern on the substrate.
Typically the toner has a thermoplastic component, and the apparatus further comprises means for preheating the toner on the substrate just prior to it entering the nip to render the thermoplastic component tacky. The means for feeding the foil strip to and past the nip and taking up the foil strip backing preferably comprises a stepper motor and motion control driver.
One of the transfer cylinders and impression cylinders is hard, while the other is somewhat deformable. For example, the raised portions of the transfer cylinder are flexible, e.g. of silicone, while the impression cylinder has a rigid metal surface which engages the substrate and which may be heated. The printing means preferably comprises a variable printer such as a computer controlled MIDAX print engine.
It is the primary object of the present invention to provide for the quick and versatile production of printed substrates having colored or metallic foil over at least a part of the printing thereon. This and other objects of the invention will become clear from an inspection of the detailed description of the invention, and from the appended claims.